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United States Patent |
5,202,209
|
Winnik
,   et al.
|
April 13, 1993
|
Toner and developer compositions with surface additives
Abstract
A toner composition comprised of resin particles, pigment particles, an
optional charge enhancing additive component, or components, and a surface
additive, or additives comprised of a metal oxide containing a coating
thereover of a surfactant.
Inventors:
|
Winnik; Francoise M. (Toronto, CA);
Riske; William (Burlington, CA);
Davidson; Anthony R. (Agincourt, CA);
Gerroir; Paul J. (Oakville, CA);
Veregin; Richard P. N. (Mississauga, CA)
|
Assignee:
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Xerox Corporation (Stamford, CT)
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Appl. No.:
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782949 |
Filed:
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October 25, 1991 |
Current U.S. Class: |
430/108.5; 430/108.2; 430/108.3; 430/108.6; 430/108.7 |
Intern'l Class: |
G03G 009/083 |
Field of Search: |
430/106.6,109,110,137,138
|
References Cited
U.S. Patent Documents
4338390 | Jul., 1982 | Lu | 430/106.
|
4394430 | Jul., 1983 | Jadwin et al. | 430/110.
|
4680245 | Jul., 1987 | Suematsu et al. | 430/110.
|
4937157 | Jun., 1990 | Haack et al. | 430/110.
|
5041351 | Aug., 1991 | Kitamori et al. | 430/110.
|
5080992 | Jan., 1992 | Mori et al. | 430/137.
|
Primary Examiner: Goodrow; John
Attorney, Agent or Firm: Palazzo; E. O.
Claims
What is claimed is:
1. A toner composition consisting essentially of resin particles, pigment
particles, an optional charge enhancing additive component, or components,
and a surface additive, or additives comprised of a metal oxide containing
a coating thereover of a surfactant; and wherein said additives have a
particle diameter of from about 4 to about 100 nanometers, and which
additives are prepared by mixing said surfactant and an organic solvent
immiscible with water to form a stable microemulsion with water; adding to
the mixture formed a solution of a hydrolyzing reagent and water to form a
microemulsion of water domains within a continuous phase of the organic
solvent; and adding to the microemulsion an oil soluble metal oxide
precursor which reacts with the hydrolyzing agent to form in the water
domains a metal oxide coated with said surfactant, and wherein said toner
particles possess improved flow characteristics and which toner particles
have triboelectric characteristics substantially independent of the
relative humidity.
2. A toner in accordance with claim 1 wherein the charge additive is
comprised of quaternary ammonium hydrogen bisulfates, tetraalkyl ammonium
sulfonates, distearyl dimethyl ammonium ethyl sulfate, of mixtures
thereof.
3. A toner composition consisting essentially of resin, and pigment, a
charge additive comprised of distearyl methyl hydrogen ammonium bisulfate,
trimethyl hydrogen ammonium bisulfate, triethyl hydrogen ammonium
bisulfate, tributyl hydrogen ammonium bisulfate, didodecyl methyl hydrogen
ammonium bisulfate, dihexadecyl methyl hydrogen ammonium bisulfate, or
mixtures thereof, and a surface additive comprised of a hydrophobic metal
oxide with a coating thereover of a surfactant, and wherein the surface
additive particles have a diameter of from between about 4 to about 100
nanometers; and wherein said additives have a particle diameter of from
about 4 to about 100 nanometers, and which additives are prepared by
mixing said surfactant and an organic solvent immiscible with water to
form a stable microemulsion with water; adding to the mixture formed a
solution of a hydrolyzing reagent and water to form a microemulsion of
water domains within a continuous phase of the organic solvent; and adding
to the microemulsion an oil soluble metal oxide precursor which reacts
with the hydrolyzing agent to form in the water domains a metal oxide
coated with said surfactant, and wherein said toner particles possess
improved flow characteristics and which toner particles have triboelectric
characteristics substantially independent of the relative humidity.
4. A toner in accordance with claim 3 wherein the surfactant is present in
an amount of from between about 0.05 to about 1.25 percent.
5. A toner in accordance with claim 3 wherein the metal oxide is titanium
dioxide, zirconium oxide, tin oxide, silicon dioxide, germanium oxide, or
mixtures thereof.
6. A toner in accordance with claim 5 wherein the coating is of a thickness
of from about 0.05 nanometer to about 5 nanometers.
7. A toner composition in accordance with claim 3 wherein the specific
gravity of the metal oxide coated with surfactant is from about 10 to
about 60 percent lower than that of the corresponding metal oxide without
a surfactant.
8. A toner in accordance with claim 1 wherein the surfactant is cationic,
anionic, nonionic, or mixtures thereof.
9. A toner in accordance with claim 1 wherein the surfactant is an alkyl
sulfate.
10. A toner in accordance with claim 1 wherein the surfactant is an
octylphenoxy polyethoxy ethanol.
11. A toner in accordance with claim 1 wherein the surfactant is dioctyl
sulfosuccinate sodium salt.
12. A toner in accordance with claim 1 wherein the pigment particles are
comprised of carbon black or magnetite.
13. A toner in accordance with claim 1 wherein the pigment particles are
comprised of cyan, magenta, yellow, brown, red, blue, green, or mixtures
thereof.
14. A toner in accordance with claim 3 wherein the surfactant is
octylphenoxy polyethoxy ethanol.
15. A toner in accordance with claim 3 wherein the surfactant is a dioctyl
sulfosuccinate sodium salt.
16. A toner in accordance with claim 3 wherein the pigment particles are
comprised of carbon black, or magnetite.
17. A toner in accordance with claim 3 wherein the pigment particles are
comprised of cyan, magenta, yellow, brown, red, blue, green, or mixtures
thereof.
18. A developer composition comprised of the toner of claim 1 and carrier
particles.
19. A developer composition comprised of the toner of claim 2 and carrier
particles.
20. A developer composition comprised of the toner of claim 3 and carrier
particles.
21. A developer composition in accordance with claim 18 wherein the carrier
particles include a polymeric coating thereover.
22. A developer composition in accordance with claim 19 wherein the carrier
particles include a polymeric coating thereover.
23. A developer composition in accordance with claim 19 wherein the carrier
particles include a mixture of polymeric coatings thereover.
24. A developer composition in accordance with claim 19 wherein the carrier
particles include a mixture of polymeric coatings thereover comprised of
polyvinylidene fluoride and polymethylmethacrylate.
25. A toner composition in accordance with claim 3 wherein the charge
additive is comprised of a chromium salicylic acid complex, a cobalt
salicylic acid complex, a zinc salicylic acid complex, a nickel salicylic
acid complex, or mixtures thereof.
26. A toner composition in accordance with claim 3 wherein the charge
additive is comprised of a sodium tetraphenyl borate or potassium
tetraphenyl borate.
27. A toner composition in accordance with claim 1 wherein the resin
particles are comprised of styrene polymers.
28. A toner composition in accordance with claim 1 wherein the resin
particles are comprised of styrene acrylates, styrene methacrylates,
styrene butadienes, or polyesters.
29. A toner composition in accordance with claim 2 wherein the resin
particles are comprised of styrene acrylates, styrene methacrylates,
styrene butadienes, or polyesters.
30. A toner composition in accordance with claim 3 wherein the resin is
comprised of styrene acrylates, styrene methacrylates, styrene butadienes,
or polyesters.
31. A toner in accordance with claim 3 wherein the surfactant is octyl
phenoxy polyethoxy ethanol and the oxide is tin oxide obtained from a
tetrabutyl stannate.
32. A toner in accordance with claim 3 wherein the surfactant is dioctyl
sulfosuccinate sodium salt and the oxide is tin oxide obtained from a
tetraisopropyl stannate.
33. A toner in accordance with claim 15 wherein the oxide is titanium
oxide, zirconium oxide, or silicon oxide.
Description
BACKGROUND OF THE INVENTION
The invention is generally directed to toner and developer compositions,
and more specifically, the present invention is directed to toner
compositions containing optional charge enhancing additives, which impart
or assist in imparting a positive or negative charge to the toner resin
particles and can enable toners with rapid admix characteristics; and
surface additives. In one embodiment, there are provided in accordance
with the present invention toner compositions comprised of resin
particles, pigment particles, a charge additive or charge additives such
as quaternary ammonium hydrogen bisulfates, including distearyl methyl
hydrogen ammonium bisulfate, orthohalophenylbenzoic acids, aluminum
complexes, reference U.S. Pat. No. 4,845,003, and copending patent
application U.S. Ser. No. 755,919, the disclosure of which is totally
incorporated herein by reference, and as surface additives metal oxides
coated with a surfactant to provide, for example, toners with improved
flow characteristics and of triboelectrical properties substantially
independent of the relative humidity of the environment. In one
embodiment, the present invention is directed to toners with surface
additives comprised of metal oxides, such as hydrophobic oxides, like tin
oxide, with a continuous coating of a surfactant, such as TRITON
X-114.RTM. which is an octylphenoxy polyethoxy ethanol surfactant, or an
AOT.RTM. surfactant which is dioctyl sulfosuccinate, sodium salt,
available from Aldrich Chemical Company, and wherein the surface additives
are particles in a uniform size with a diameter of, for example, from
between about 3 to about 100 nanometers and preferably from about 3 to
about 50 nanometers as determined by transmission electron microscopy.
Also, the aforementioned toner compositions usually contain pigment
particles comprised of, for example, carbon black, magnetites, or mixtures
thereof, cyan, magenta, yellow, blue, green, red, or brown components, or
mixtures thereof thereby providing for the development and generation of
black and/or colored images. The toner compositions of the present
invention in embodiments thereof possess excellent admix characteristics
as indicated herein, and maintain their triboelectric charging
characteristics for an extended number of imaging cycles exceeding, for
example, 500,000 in a number of embodiments. The toner and developer
compositions of the present invention can be selected for
electrophotographic, especially xerographic imaging and printing
processes, including color processes, such as trilevel and full color
process xerography, reference for example copending patent application
U.S. Ser. No. 705,995, the disclosure of which is totally incorporated
herein by reference.
Toner compositions with surface additives, such as silica like AEROSIL
R972.RTM., are known. These additives, which may have a small particle
size diameter of 7 to 100 nanometers, may adversely effect the sign,
magnitude, and stability of the toner triboelectric charging and wherein
the developer charge becomes highly dependent on the relative humidity,
disadvantages avoided, or minimized with the invention of the present
application. Other disadvantages associated with the prior art surface
additives include the high specific gravity of the additives which ranges
from about 2.2 grams/cm.sup.3 for silica flow additives to about 4
grams/cm.sup.3 for titania additives. The additives of the present
invention can achieve specific gravities approaching about 1.2
grams/cm.sup.3. Reducing the specific gravity of a flow aid, for example,
from about 6.95 grams per cm.sup.3 for tin oxide produced by the flame
hydrolysis process to about 3.2 grams per cm.sup.3 for tin oxide selected
for the toners of the present invention results in a decrease from about
2.0 to about 0.8 in the weight percent of flow aid needed to achieve
superior flow of a toner, since the effectiveness of a flow aid depends on
its surface area and not on its mass. Therefore, less flow aid is
required, resulting in a lowering of the cost of the toner proportional to
the lowering of the mass of the flow aid used in a toner composition.
Moreover, a lowering of the amount of flow aids will reduce undesired
contamination of other components of a xerographic imaging apparatus, such
as the Xerox Corporation 5090.RTM., especially the photoconductive imaging
member and the fuser components.
The use of small fumed silica particles of diameter ranging from about 7 to
about 100 nanometers for the improvement of toner flow properties is
known. These materials such as, for example, AEROSIL 380.RTM. available
from Degussa, as well as other inorganic oxides, such as for example
titania, available from Degussa as DEGUSSA P25.RTM. or alumina, available
from Degussa as DEGUSSA ALUMINUM OXIDE C.RTM., are invariably produced by
a flame hydrolysis process. One disadvantage of the use of such materials
is that they are hydrophilic and thus are sensitive to environment
humidity, resulting in a decrease in flow and in triboelectric charge of
the toner with increasing humidity. For example, a 50 percent decrease in
flow and a 50 percent decrease in charge take place as the humidity of the
environment reaches 80 percent RH. A well-known process to reduce the
humidity sensitivity of these materials is the surface treatment of the
inorganic oxides with a functional silane, such as for example
hexadimethylsilane, dimethyldichlorosilane, methyltrichlorosilane, and
trimethylchlorosilane. Other surface treatments and/or combinations of
different inorganic oxides have also been shown in the prior art. For
example, Japanese Publication (JP) 61 250,658 discloses mixtures of
negatively and positively charging silicas for toner flow improvement,
while Japanese Publication 61 249,059 discloses the use of mixtures of
hydrophilic and hydrophobic silicas for improved toner flow.
Similarly, Japanese Publication 62 227,140 discloses the use of negative
toners coated in a first step with a positive charge additive, such as,
for example, alumina treated with an amine-modified silicone oil and in a
second step with a negative charge additive, such as, for example, a
silica treated with dimethyldichlorosilane, for improved flow. Another
surface treatment for silica has been disclosed in U.S. Pat. No. 4,680,245
which illustrates an aminosilane-treated silica for positive charging of
toners. The Japanese patent Japanese Publication 62 172,372 discloses the
use of a hydrophilic titania treated with a zirconium aluminum coupling
agent to obtain negatively charged toners.
The aforementioned surface treatments of inorganic oxides using
hydrolyzable silanes or other coupling agents and the application of this
treatment for the modification of the surface properties of inorganic
oxides produced by the flame hydrolysis process possess a number of
disadvantages when selected for toners. One of the disadvantages
associated with the use of such surface-treated inorganic oxides is that
their use often results in changes in the charging properties of the
toner, resulting in an undesirable lowering by, for example, 30
microcoulombs per gram or raising by, for example, 20 microcoulombs per
gram of the toner charge. Moreover, the use of these surface-treated
additives also results often in a decrease by, for example, 30 percent of
the stability of the toner charge particularly under high humidity
conditions, for example 85 percent. These and other disadvantages are
avoided with the toners of the present invention.
P. Espiard et al., "A Novel Technique for Preparing Organophilic Silica by
Water-In-Oil Microemulsions," Polymer Bulletin, vol. 24, pages 170 to 173
(Spring 1990), the disclosure of which is totally incorporated herein by
reference, discloses a technique for preparing ultramicro spherical silica
particles containing vinyl groups on their surfaces by a combination of
the sol-gel technique and the water-in-oil emulsion technique in which
hydrolysis and condensation of tetraethyl siloxane and
trimethoxysilylpropyl methacrylate take place. Spherical silica particles
with a size range from 20 to 70 nanometers were obtained and the surface
concentrations of the double bonds per square nanometer were from 4 to 7.
H. Yamauchi et al., "Surface Characterization of Ultramicro Spherical
Particles of Silica Prepared by W/O Microemulsion Method", Colloids and
Surfaces, vol. 37, pages 71 to 80 (1989), the disclosure of which is
totally incorporated herein by reference, discloses the preparation of
ultramicro spherical particles of colloidal silica by the hydrolysis of
tetraethoxysilane in the water pool of a water-in-oil (isooctane)
microemulsion using Aerosol-OT. The average diameter of the silica spheres
obtained was of the order of 10 nanometers and their surface areas were
about 100 to 300 square meters per gram. The nitrogen adsorption isotherms
of this material indicate that the particles have micropores in contrast
to colloidal nonporous silica particles such as AEROSILS.RTM. and those in
silica sols having a similar size of particle.
J.C. Giuntini et al., "Sol-gel preparation and transport properties of a
tin oxide", Journal of Materals Science Letters, vol. 9, pages 1383 to
1388 (1990), the disclosure of which is totally incorporated herein by
reference, disclosed a technique for preparing tin alkoxide by hydrolysis
of tin butylate to a tin oxide gel.
Also, developer compositions with charge enhancing additives, which impart
a positive charge to the toner resin, are well known. Thus, for example,
there is described in U.S. Pat. No. 3,893,935 the use of quaternary
ammonium salts as charge control agents for electrostatic toner
compositions. In this patent, there are disclosed quaternary ammonium
compounds with four R substituents on the nitrogen atom, which
substituents represent an aliphatic hydrocarbon group having 7 or less,
and preferably about 3 to about 7 carbon atoms, including straight and
branch chain aliphatic hydrocarbon atoms, and wherein X represents an
anionic function including, according to this patent, a variety of
conventional anionic moieties such as halides, phosphates, acetates,
nitrates, benzoates, methylsulfates, perchloride, tetrafluoroborate,
benzene sulfonate, and the like; U.S. Pat. No. 4,221,856 which discloses
electrophotographic toners containing resin compatible quaternary ammonium
compounds in which at least two R radicals are hydrocarbons having from 8
to about 22 carbon atoms, each other R is a hydrogen or hydrocarbon
radical with from 1 to about 8 carbon atoms, and A is an anion, for
example, sulfate, sulfonate, nitrate, borate, chlorate, and the halogens
such as iodide, chloride and bromide, reference the Abstract of the
Disclosure and column 3; a similar teaching is presented in U.S. Pat. No.
4,312,933 which is a divisional of U.S. Pat. No. 4,291,111; and similar
teachings are presented in U.S. Pat. No. 4,291,112 wherein A is an anion
including, for example, sulfate, sulfonate, nitrate, borate, chlorate, and
the halogens. There are also described in U.S. Pat. No. 2,986,521 reversal
developer compositions comprised of toner resin particles coated with
finely divided colloidal silica. According to the disclosure of this
patent, the development of electrostatic latent images on negatively
charged surfaces is accomplished by applying a developer composition
having a positively charged triboelectric relationship with respect to the
colloidal silica.
Also, there is disclosed in U.S. Pat. No. 4,338,390, the disclosure of
which is totally incorporated herein by reference, developer compositions
containing as charge enhancing additives organic sulfate and sulfonates,
which additives can impart a positive charge to the toner composition.
Further, there are disclosed in U.S. Pat. No. 4,298,672, the disclosure of
which is totally incorporated herein by reference, positively charged
toner compositions with resin particles and pigment particles, and as
charge enhancing additives alkyl pyridinium compounds. Additionally, other
documents disclosing positively charged toner compositions with charge
control additives include U.S. Pat. Nos. 3,944,493; 4,007,293; 4,079,014
4,394,430, and 4,560,635 which illustrates a toner with a distearyl
dimethyl ammonium methyl sulfate charge additive.
Moreover, toner compositions with negative charge enhancing additives are
known, reference for example U.S. Pat. Nos. 4,411,974 and 4,206,064, the
disclosures of which are totally incorporated herein by reference. The
'974 patent discloses negatively charged toner compositions comprised of
resin particles, pigment particles, and as a charge enhancing additive
ortho-halo phenyl carboxylic acids. Similarly, there are disclosed in the
'064 patent toner compositions with chromium, cobalt, and nickel complexes
of salicylic acid as negative charge enhancing additives.
Illustrated in U.S. Pat. No. 4,937,157, the disclosure of which is totally
incorporated herein by reference, are toner compositions comprised of
resin, pigment, or dye, and tetraalkyl, wherein alkyl, for example,
contains from 1 to about 30 carbon atoms, ammonium bisulfate charge
enhancing additives such as distearyl dimethyl ammonium bisulfate,
tetramethyl ammonium bisulfate, tetraethyl ammonium bisulfate, tetrabutyl
ammonium bisulfate, and preferably dimethyl dialkyl ammonium bisulfate
compounds where the dialkyl radicals contain from about 10 to about 30
carbon atoms, and more preferably dialkyl radicals with from about 14 to
about 22 carbon atoms, and the like. The aforementioned charge additives
can be incorporated into the toner or may be present on the toner surface.
Advantages of rapid admix, appropriate triboelectric characteristics, and
the like are achieved with many of the toners of the aforementioned
copending application.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide toner and developer
compositions with many of the advantages illustrated herein.
In another object of the present invention there are provided positively
charged toner compositions useful for the development of electrostatic
latent images including color images.
In yet another object of the present invention there are provided
positively charged toner compositions containing quaternary ammonium
hydrogen bisulfate, especially trialkyl ammonium hydrogen bisulfate,
charge enhancing additives.
In yet another object of the present invention there are provided
negatively charged toner compositions containing, for example, metal
tetraphenyl borate such as potassium tetraphenyl borate and sodium
tetraphenyl borate and metal salicylates, such as the chromium complex of
alkyl salicylic acids and the zinc complex of alkyl salicylic acids.
In yet another object of the present invention there are provided toner
compositions with surface additives of metal oxides coated with a
surfactant to enable toners with improved flow characteristics.
Another object of the present invention resides in providing toner
compositions with surface additives to enable toners with suitable flow
together with stability of their triboelectric charge with changes in
humidity, for example from between about 20 to 80 percent in embodiments.
Another object of the present invention resides in providing colored toner
compositions with surface additives with an average diameter of from
between about 3 to about 100 nanometers.
In yet a further object of the present invention there are provided
humidity insensitive, from about, for example, 20 to 80 percent relative
humidity at temperatures of from 60.degree. to 80.degree. F. as determined
in a relative humidity testing chamber, toner compositions with desirable
admix properties of 5 seconds to 60 seconds as determined by a charge
spectrograph, and preferably less than 15 seconds for example, and more
preferably from about 1 to about 14 seconds, and acceptable triboelectric
charging characteristics of from about 10 to about 40 microcoulombs per
gram.
Additionally, in a further object of the present invention there are
provided positively charged magnetic toner compositions, and positively
charged colored toner compositions containing therein, or thereon
quaternary ammonium hydrogen bisulfate, especially trialkyl ammonium
hydrogen bisulfate charge enhancing additives or tetraalkyl ammonium
sulfonates, such as dimethyl distearyl ammonium sulfonate charge enhancing
additives, and surface additives of metal oxides coated with a surfactant.
In another object of the present invention that are provided processes for
the preparation of the surface additives.
Another object of the present invention resides in the formation of toners
which will enable the development of images in electrophotographic imaging
apparatuses, which images have substantially no background deposits
thereon, are substantially smudge proof or smudge resistant, and therefore
are of excellent resolution; and further, such toner compositions can be
selected for high speed electrophotographic apparatuses, that is those
exceeding 70 copies per minute.
Another object of the present invention is to provide processes for the
preparation of oxides with a specific gravity of from about 1.0 to about
6.0, a value which is less than the specific gravity of similar oxides
produced by other methods known in the art.
Yet in another object of the present invention there are provided toner
compositions with excellent flow but with reduced loadings of surface
additives, for example a reduction of 50 percent in the weight percent
loading, compared to toner compositions known in the prior art, such as a
toner compositions comprised of 2.7 percent by weight of T-25 titanium
oxide obtained from Degussa and 97.3 percent by weight of a toner
comprised of 50 percent by weight of styrene and 50 percent by weight of
n-butyl methacrylate, 6 percent by weight of REGAL 330.RTM. carbon black
and 0.5 percent by weight of cetyl pyridinium chloride.
These and other objects of the present invention can be accomplished in
embodiments thereof by providing toner compositions comprised of resin
particles, pigment particles, optional charge enhancing additives
comprised, for example, of quaternary ammonium hydrogen bisulfates, tetra
alkyl ammonium sulfonates, distearyl dimethyl ammonium ethyl sulfate, and
the like, and surface additives comprised of a metal oxide containing a
coating thereover of a surfactant. More specifically, the present
invention in one embodiment is directed to toner compositions comprised of
resin, pigment, or dye, an optional known charge additive or additives,
such as distearyl methyl hydrogen ammonium bisulfate, trimethyl hydrogen
ammonium bisulfate, triethyl hydrogen ammonium bisulfate, tributyl
hydrogen ammonium bisulfate, didodecyl methyl hydrogen ammonium bisulfate,
dihexadecyl methyl hydrogen ammonium bisulfate, and preferably distearyl
methyl hydrogen ammonium bisulfate, or mixtures of charge additives, such
as the forementioned bisulfates with distearyl dimethyl ammonium
methylsulfate, the bisulfates, and charge additives of U.S. Pat. No.
4,937,157 and U.S. Pat. No. 4,904,762 and copending application U.S. Ser.
No. 396,497, the disclosures of which are totally incorporated herein by
reference, the charge additives of the patents mentioned herein; and the
like; and hydrophobic metal oxides with a coating thereover of a
surfactant, and wherein the surface additive particles have a diameter of
from about 4 to about 100 nanometers and preferably from about 5 to about
30 nanometers. In another embodiment, the present invention is directed to
a process for preparing surface additive particles which comprises
preparing a mixture of a surfactant and an organic solvent immiscible with
water and capable of forming a stable microemulsion with water, adding to
the mixture a solution of a hydrolyzing reagent and water to form a
microemulsion of water domains within a continuous phase of the organic
solvent, and adding to the microemulsion an oil-soluble metal oxide
precursor, which reacts with the hydrolyzing agent to form in each water
domain a metal oxide particle coated with the surfactant.
In embodiments, the toners can contain charge additives comprised of
chromium salicylic acid complexes, cobalt salicylic acid complexes, zinc
salicylic acid complexes, nickel salicylic acid complexes and preferably
chromium salicylic acid complexes or mixtures thereof, with hydrophobic
metal oxides with a coating thereover of a surfactant, and wherein the
surface additive particles have a diameter of from between about 4 to
about 100 nanometers. Also, charge additives include odium tetraphenyl
borate or potassium tetraphenyl borate, and preferably sodium tetraphenyl
borate, or mixtures thereof, with hydrophobic metal oxides with a coating
thereover of a surfactant, and wherein the surface additive particles have
a diameter of from between about 4 to about 100 nanometers.
In another embodiment of the present invention, there are provided,
subsequent to known micronization and classification to enable toner
particles with an average diameter of from about 5 to about 20 microns,
toners comprised of resin particles, pigment particles, and charge
enhancing additives; and the surface additives can then be subsequently
blended thereon.
Examples of surface additive particles present in effective amounts such
as, for example, from between 0.05 to about 1.25 percent by weight of
toner and preferably from between 0.1 to about 1.0 percent by weight of
toner include hydrophobic oxides, such as titania, zirconia, silica,
germanium oxide or mixed oxides, and the like coated with a surfactant.
The coating is of an effective thickness of, for example, from about 0.05
nanometer to about 5 nanometers and preferably from about 0.1 to about 2
nanometers. Examples of suitable surfactants include cationic, anionic, or
nonionic types. Suitable anionic surfactants include alkyl sulfates of the
general structure R.sup.1 OSO.sup.3 M, where R.sup.1 is alkyl with from
about 1 to about 25 carbon atoms, such as n-hexyl, n-octyl, n-nonyl,
n-decyl, n-undecyl, or n-dodecyl, and M is a cation, such as, for example
an alkali metal, like, sodium or potassium cation, alkyl sulfonates of the
general structure R.sup.1 SO.sup.3 M, where R.sup.1 is alkyl such as
n-hexyl, n-octyl, n-monyl, n-decyl, n-undecyl, or n-dodecyl, and M is a
cation, such as for example sodium or potassium cation, aryl sulfates of
the general structure Ar.sup.1 OSO.sup.3 M, where Ar.sup.1 is an R.sup.1
alkyl substituted aryl, such as phenyl, aryl sulfonates of the general
structure Ar.sup.1 SO.sup.4 M, where Ar.sup.1 is an alkyl substituted
aryl, such as phenyl, the alkyl group being represented by R.sub.1,
dialkylsulfates of the general structure R.sub.3 COOCH.sub.2
CHZ--OOC--R.sub.3, where R.sub.3 is n-butyl, n-pentyl, n-hexyl, n-heptyl,
or n-octyl and Z is a sulfonate group, dialkylsulfates of the general
formula R.sub.3 OCH.sub.2 CH(SO.sub.4 M)CH.sub.2 OR.sub.3, wherein R.sub.3
is alkyl, and the like. Suitable cationic surfactants include
alkylammonium salts of the general structure R.sub.2 N+(CH.sub.3).sub.2
X--, where R.sub.2 is n-hexyl, n-octyl, n-nonyl, n-decyl, n-undecyl,
n-dodecyl, n-tetradecyl, n-hexadecyl, or n-octadecyl, and X-- is a halogen
anion such as a chloro or bromo anion, alkylammonium salts of the general
formula R.sub.2 NH.sub.2 +X--, where R.sub.2 is n-hexyl, n-octyl, n-nonyl,
n-decyl, n-undecyl, n-dodecyl, n-tetradecyl, n-hexadecyl, or n-octadecyl,
and X-- is a halogen anion such as a chloro or bromo anion, alkyl
pyridinium salts of the general formula Ar.sub.2 +X--, where Ar.sub.2 is
an alkyl substituted pyridinium group, the alkyl group represented by
R.sub.2, dialkylammonium salts of the general structure (R2).sub.2
(CH.sub.3).sub.2 N+X--, dialkylammonium salts of the general formula
(R.sub.2).sub.2 H.sub.2 N+X--, wherein R.sub.2 is alkyl and X is a
halogen, and the like. Suitable neutral surfactant include compounds of
the general formula Ar.sub.3 --O--(CH.sub.2 CH.sub.2 O).sub.n H, where
Ar.sub.3 is an alkyl substituted phenyl group, the alkyl group belonging
to the group represented by R.sub.2 or branched alkyl groups such as
1,1,3,3-tetramethylbutyl, and n is a number ranging from about one to
about 20, R.sub.4 --O--(CH.sub.2 CH.sub.2 O).sub.n H, where R.sub.4 is an
alkyl substituted cyclohexyl group, the alkyl group being represented by
R.sub.2 or branched alkyl groups such as 1,1,3,3-tetramethylbutyl, and n
is a number ranging from about one to about 20, R.sub.2 CO--O--(CH.sub.2
CH.sub.2 O).sub.n H, and R.sub.2 is alkyl, where n is a number ranging
from about one to about 20, glucosides of general structure R.sub.2 --G,
where G is a glucopyranoside substituted at the anomeric position with an
alkoxy group of general structure OR.sub.2, and wherein R.sub.2 is alkyl,
thioglucosides of general structure R.sub.2 --SG, where SG is a
thioglucopyranoside substituted at the anomeric position with an alkyl
thio group of general structure SR.sub.2, and the like. Specific examples
of suitable commercial surfactants include those of the TRITON.RTM. series
available from Rohm and Haas Company, those of the TERGITOL.RTM. series
available from Union Carbide Corporation, and those of the TEEPOL.RTM.
series available from Shell Chemical Company.
The surface additives of the present invention can be prepared by the
hydrolysis of an oil-soluble metal oxide precursor in stable water-in-oil
microemulsions comprised of water, an organic solvent immiscible with
water and capable of forming a stable microemulsion in water, a
hydrolyzing agent and one or more surfactants. The oil-soluble metal oxide
precursor is readily hydrolyzed by the hydrolyzing agent in the water
droplets, resulting in the formation of metal oxide particles entrapped
within the existing surfactant-coated water droplets. Isolation of the
surfactant coated oxide from the microemulsion can be accomplished by a
number of known methods, such as precipitation, filtration, and drying.
Examples of suitable organic solvents include aliphatic hydrocarbons, such
as n-hexane, n-heptane, n-octane, n-decane, n-dodecane, iso-heptane,
iso-octane, isopar-M, cyclopentane, cyclohexane, cycloheptane,
methyl-cyclohexane, aromatic hydrocarbons, such as benzene, toluene,
o-xylene, m-xylene, p-xylene, ethyl-benzene, 1,3,5-trimethylbenzene
substituted aromatic hydrocarbons, such as chlorobenzene, bromobenzene,
1-bromonaphthalene. The organic solvent is present in any effective
amount; typically, the organic solvent is present with respect to the
water in a ratio between about 1 part organic solvent to about 1 part
water and about 15 parts organic solvent to about 1 part water, and
preferably is present with respect to the water in a ratio between about 3
parts organic solvent to about 1 part water and about 10 parts organic
solvent to about 1 parts water, although the organic-to-water ratio can be
outside of this range in embodiments.
Examples of suitable oil-soluble metal oxide precursors include
tetraalkoxytitanates, tetraalkoxystannates, tetraalkoxyzirconates,
tetraalkoxygermanates, tetraalkoxysilanes, and the like. Examples of
suitable tetraalkoxytitanates for the process of the present invention
include those with from 1 to 18 carbon atoms in the alkyl portion, such as
tetramethoxytitanate, tetraethoxytitanate, tetra-n-propoxytitanate,
tetra-i-propoxytitanate, tetra-n-butoxytitanate, tetra-s-butoxytitanate,
tetrapentoxytitanate, tetra-n-hexyloxytitanate, tetraoctyloxytitanate,
tetradecyloxy, titanate tetradodecyloxytitanate,
tetraoctadecyloxytitanate, and the like. Examples of suitable
tetraalkoxyzirconates for the process of the present invention include
those with from 1 to 18 carbon atoms in the alkyl portion, such as
tetramethoxyzirconate, tetraethoxyzirconate, tetra-n-propoxyzirconate,
tetra-i-propoxyzirconate, tetra-n-butoxyzirconate, tetra-s-butoxy,
tetrapentoxyzirconate, tetra-n-hexyloxyzirconate, tetraoctyloxyzirconate,
tetradecyloxyzirconate, tetradodecyloxyzirconate,
tetraoctadecyloxyzirconate, and the like. Examples of suitable
tetraalkoxystannates for the process of the present invention include,
those with from 1 to 18 carbon atoms in the alkyl portion, such as
tetramethoxystannate, tetraethoxystannate, tetra-n-propoxystannate,
tetra-i-propoxystannate, tetra-n-butoxystannate, tetra-s-butoxystannate,
tetrapentoxystannate, tetra-n-hexyloxystannate, tetraoctyloxystannate,
tetradecyloxystannate, tetradodecyloxystannate, tetraoctadecyloxystannate,
and the like. Examples of suitable tetraalkoxy germanates for the process
of the present invention include, those with from 1 to 18 carbon atoms in
the alkyl portion, such as tetramethoxygermanate, tetraethoxygermanate,
tetra-n-propoxygermanate, tetra-i-propoxygermanate,
tetra-n-butoxygermanate, tetra-s-butoxygermanate, tetrapentoxygermanate,
tetra-n-hexyloxygermanate, tetraoctyloxygermanate, tetradecyloxygermanate,
tetradodecyloxygermanate, tetraoctadecyloxygermanate, and the like.
Examples of suitable tetraalkoxysilanes for the process of the present
invention include those with from 1 to about 6 carbon atoms in the alkyl
portion, such as tetramethoxysilane, tetraethoxysilane,
tetra-n-propoxysilane, tetra-i-propoxysilane, tetra-n-butoxysilane,
tetra-s-butoxysilane, tetra-i-butoxysilane, tetrapentoxysilane,
tetrakis-(2-methoxyethoxysilane), and the like. The tetraalkoxysilane is
added to the water-in-oil emulsion in any effective amount; typically, the
tetraalkoxysilane is present in an amount of from about 1 to about 30
percent by weight of the water phase, and preferably is present in an
amount of from about 5 to about 15 percent by weight of the water phase,
although the amount can be outside of this range.
Examples of suitable reagents for hydrolyzing the oil-soluble metal oxide
precursor include water-soluble bases such as ammonium hydroxide, sodium
hydroxide, potassium hydroxide, organic amines such as methyl amine, ethyl
amine, and propyl amine, or the like. The hydrolyzing reagent is added to
the water-in-oil emulsion in any effective amount; typically, the
hydrolyzing reagent is present in an amount of from about 10 to about 60
percent by weight of the water phase, and preferably is present in an
amount of from about 20 to about 40 percent by weight of the water phase,
although the amount can be outside of this range.
The surface additive particles of the present invention can be prepared by
first mixing together the surfactant and the organic solvent (oil phase),
followed by adding water to the mixture and stirring until a stable
microemulsion is formed. The microemulsion can be formed by stirring or
gently shaking the solution at room temperature, although the solution can
also be heated or cooled if desired. The microemulsion has completed
formation when turbidity disappears from the solution and the solution
appears to contain a single phase; the emulsion is microscopic and not
visible to the unaided eye. Subsequent to formation of the microemulsion,
the oil-soluble metal oxide precursor is added, preferably dropwise, and
the microemulsion is stirred until the reaction is complete. The reaction
can take place at room temperature, although the microemulsion can also be
heated or cooled if desired. The reaction can take place for a period
ranging from about 4 hours to about 48 hours. Upon completion of the
reaction, the surface additive particles thus formed are recovered from
the solution. Recovery can be by any suitable means, such as by adding to
the microemulsion a solvent that breaks up the microemulsion, such as
acetone, methanol, ethanol, ethyl acetate, butyl acetate, methyl
cellosolve, ethyl cellosolve, followed by filtering out the particles that
precipitate from the solution, and washing and drying the particles. The
surface additive particles can also be recovered by evaporating the
solvent to leave the particles as a solid residue, by spray drying, or the
like.
Optionally, the surface additive particles of the present invention can be
prepared by first mixing together the surfactant and the organic solvent
(oil phase), followed by adding to the mixture a solution of a hydrolyzing
agent in water and stirring until a stable microemulsion is formed. The
microemulsion can be formed by stirring or gently shaking the solution at
room temperature, although the solution can also be heated or cooled if
desired. The microemulsion has completed formation when turbidity
disappears from the solution and the solution appears to contain a single
phase; the emulsion is microscopic and not visible to the unaided eye.
Subsequent to formation of the microemulsion, the oil-soluble metal oxide
precursor is added, preferably dropwise, and the microemulsion is stirred
until the reaction is complete. The reaction can take place at room
temperature, although the microemulsion can also be heated or cooled if
desired. The reaction can be accomplished in a period of from about 4
hours to about 48 hours. Upon completion of the reaction, the surface
additive particles thus formed are recovered from the solution. Recovery
can be by any suitable means, such as by adding to the microemulsion a
solvent that breaks up the microemulsion, such as acetone, methanol,
ethanol, ethyl acetate, butyl acetate, methyl cellosolve, ethyl
cellosolve, followed by filtering out the particles that precipitate from
the solution and washing and drying the particles. The surface additive
particles can also be recovered by evaporating the solvent to leave the
particles as a solid residue, by spray drying, or the like.
Surface additive particles of the present invention typically have an
average particle diameter of from about 3 to about 100 nanometers, and
preferably from about 5 to about 50 nanometers, although the average
particle diameter can be outside this range. Particle size can be
controlled primarily by the ratio of oil to water employed in the
microemulsion, although other ingredients in the microemulsion, such as a
cosurfactant or cosolvent, can also be present to control drop size
provided that they do not inhibit the reaction. Examples of cosolvents
include alkyl alcohols, such as methanol, ethanol, n-propanol, n-butanol,
n-pentanol, n-hexanol, n-heptanol, or n-octanol, 2-methyl-2-hexanol, and
cyclohexanol, alkenols, such as 9-decenol, aryl alcohols, such as
3-phenylpropanol, diols, such as 3-phenoxy-1,2-propanediol. Mixtures of
two or more surfactants may be used as long as they satisfy the
requirements necessary for microemulsion formation as described, for
example, by J. M. Williams, Langmuir, 7, 1370 to 1377 (1991) and
references therein.
The chemical composition of the surface additives of the present invention
can be determined by a number of analytical techniques, including, for
example, elemental analysis, thermal gravimetric analysis, Energy
Dispersive X-Ray Analysis. Tipically, the particles comprise a metal oxide
in an amount of from about 40 to about 95 percent by weight and a
surfactant in an amount of from about 5 to about 60 percent by weight,
although the amounts can be outside these ranges. The amount of surfactant
is controlled primarily by the ratio of surfactant to water employed in
the microemulsion, although other factors may be important as well, such
as for example the chemical composition and the amount of solvent added to
the microemulsion to recover the particles upon completion of the
reaction.
Optionally, the surface additives of the present invention can be treated
with from about 2 to about 100 weight percent, and preferably from about 5
to about 30 weight percent with a hydrolyzable silane, such as for example
hexamethyldisilazane, dimethyl dichlorosilane, methyltrichlorosilane,
trimethyl chlorosilane, methyl diethoxysilane, dimethyl dimethoxy silane,
trimethyl methoxy silane, and the like. This treatment may be performed,
for example, by reaction of the hydrolyzable silane with a dispersion of
the additive in a solvent on the surfactant-coated surface additives of
the present invention.
The toner compositions of the present invention can be prepared by a number
of known methods such as admixing and heating resin particles such as
styrene butadiene copolymers, pigment particles such as magnetite, carbon
black, or mixtures thereof, and preferably from about 0.5 percent to about
5 percent of the aforementioned charge enhancing additives, or mixtures of
charge additives, in a toner extrusion device, such as the ZSK53 available
from Werner Pfleiderer, and removing the formed toner composition from the
device. Subsequent to cooling, the toner composition is subjected to
grinding utilizing, for example, a Sturtevant micronizer for the purpose
of achieving toner particles with a volume median diameter of less than
about 25 microns, and preferably of from about 8 to about 12 microns,
which diameters are determined by a Coulter Counter. Subsequently, the
toner compositions can be classified utilizing, for example, a Donaldson
Model B classifier for the purpose of removing fines, that is toner
particles less than about 4 microns volume median diameter. Thereafter,
the surface additive of the metal oxide with the surfactant coating is
added to the toner by, for example, dry mixing the toner with from about
0.2 to about 2 percent by weight of the metal oxide using a paint shaker,
roll-milling the toner and the metal oxide in a bottle containing metal or
plastic balls, blending the toner and the metal oxide in a blender
equipped with a blade moving at a speed of from about 10 meters per second
to about 100 meters per second. Alternatively, the metal oxide and the
toner can be dispersed in water, and subsequently, a toner composition can
be obtained by drying the resulting suspension by processes such as, for
example, air drying or spray drying.
Illustrative examples of suitable toner resins selected for the toner and
developer compositions of the present invention include polyamides,
polyolefins, styrene acrylates, styrene methacrylate, styrene butadienes,
crosslinked styrene polymers, epoxies, polyurethanes, vinyl resins,
including homopolymers or copolymers of two or more vinyl monomers; and
polymeric esterification products of a dicarboxylic acid and a diol
comprising a diphenol. Vinyl monomers include styrene, p-chlorostyrene,
unsaturated mono-olefins such as ethylene, propylene, butylene,
isobutylene and the like; saturated mono-olefins such as vinyl acetate,
vinyl propionate, and vinyl butyrate; vinyl esters like esters of
monocarboxylic acids including methyl acrylate, ethyl acrylate,
n-butylacrylate, isobutyl acrylate, dodecyl acrylate, n-octyl acrylate,
phenyl acrylate, methyl methacrylate, ethyl methacrylate, and butyl
methacrylate; acrylonitrile, methacrylonitrile, acrylamide; mixtures
thereof; and the like. Styrene butadiene copolymers with a styrene content
of from about 70 to about 95 weight percent, reference the U.S. patents
mentioned herein, the disclosures of which have been totally incorporated
herein by reference, can be selected in embodiments. In addition,
crosslinked resins, including polymers, copolymers, homopolymers of the
aforementioned styrene polymers, may be selected.
As one toner resin, there can be selected the esterification products of a
dicarboxylic acid and a diol comprising a diphenol. These resins are
illustrated in U.S. Pat. No. 3,590,000, the disclosure of which is totally
incorporated herein by reference. Other specific toner resins include
styrene/methacrylate copolymers, and styrene/butadiene copolymers;
PLIOLITES.RTM.; suspension polymerized styrene butadienes, reference U.S.
Pat. No. 4,558,108, the disclosure of which is totally incorporated herein
by reference; polyester resins obtained from the reaction of Bisphenol A
and propylene oxide; followed by the reaction of the resulting product
with fumaric acid, and branched polyester resins resulting from the
reaction of dimethylterephthalate, 1,3-butanediol, 1,2-propanediol, and
pentaerythritol, styrene acrylates, and mixtures thereof. Also, waxes with
a molecular weight of from between about 1,000 to about 6,000 such as
polyethylene, polypropylene, and paraffin waxes can be included in, or on
the toner compositions as fuser roll release agents.
The resin particles are present in a sufficient, but effective amount, for
example from about 70 to about 90 weight percent. Thus, when 1 percent by
weight of the charge enhancing additive is present, and 10 percent by
weight of pigment or colorant, such as carbon black, is contained therein,
about 89 percent by weight of resin is selected. Also, the charge
enhancing additive of the present invention may be coated on the pigment
particle. When used as a coating, the charge enhancing additive of the
present invention is present in an amount of from about 0.1 weight percent
to about 5 weight percent, and preferably from about 0.3 weight percent to
about 1 weight percent.
Numerous well known suitable pigments or dyes can be selected as the
colorant for the toner particles including, for example, carbon black like
REGAL 330.RTM., nigrosine dye, blue, magnetite, or mixtures thereof. The
pigment, which is preferably carbon black, should be present in a
sufficient amount to render the toner composition highly colored.
Generally, the pigment particles are present in amounts of from about 1
percent by weight to about 20 percent by weight, and preferably from about
2 to about 10 weight percent based on the total weight of the toner
composition; however, lesser or greater amounts of pigment particles can
be selected providing the objectives of the present invention are
achieved.
When the pigment particles are comprised of magnetites, thereby enabling
single component toners in some instances, which magnetites are a mixture
of iron oxides (FeO.Fe.sub.2 O.sub.3) including those commercially
available as MAPICO BLACK.RTM., they are present in the toner composition
in an amount of from about 10 percent by weight to about 70 percent by
weight, and preferably in an amount of from about 10 percent by weight to
about 50 percent by weight. Mixtures of carbon black and magnetite with
from about 1 to about 15 weight percent of carbon black, and preferably
from about 2 to about 6 weight percent of carbon black, and magnetite,
such as MAPICO BLACK.RTM., in an amount of, for example, from about 5 to
about 60, and preferably from about 10 to about 50 weight percent can be
selected.
Also, there can be included in the toner compositions of the present
invention low molecular weight waxes, such as polypropylenes and
polyethylenes commercially available from Allied Chemical and Petrolite
Corporation, EPOLENE N-15.RTM. commercially available from Eastman
Chemical Products, Inc., VISCOL 550-P.RTM., a low weight average molecular
weight polypropylene available from Sanyo Kasei K.K., and similar
materials. The commercially available polyethylenes selected have a
molecular weight of from about 1,000 to about 1,500, while the
commercially available polypropylenes utilized for the toner compositions
of the present invention are believed to have a molecular weight of from
about 4,000 to about 5,000. Many of the polyethylene and polypropylene
compositions useful in the present invention are illustrated in British
Patent No. 1,442,835, the disclosure of which is totally incorporated
herein by reference.
The low molecular weight wax materials are present in the toner composition
of the present invention in various amounts, however, generally these
waxes are present in the toner composition in an amount of from about 1
percent by weight to about 15 percent by weight, and preferably in an
amount of from about 2 percent by weight to about 10 percent by weight.
Encompassed within the scope of the present invention in embodiments are
colored toner and developer compositions comprised of toner resin
particles, carrier particles, the charge enhancing additives illustrated
herein, and as pigments or colorants red, blue, green, brown, magenta,
cyan and/or yellow particles, as well as mixtures thereof. More
specifically, with regard to the generation of color images utilizing a
developer composition with the charge enhancing additives of the present
invention, illustrative examples of magenta materials that may be selected
as pigments include, for example, 2,9-dimethyl-substituted quinacridone
and anthraquinone dye identified in the Color Index as CI 60710, CI
Dispersed Red 15, diazo dye identified in the Color Index as CI 26050, CI
Solvent Red 19, and the like. Illustrative examples of cyan materials that
may be used as pigments include copper tetra-4-(octadecyl
sulfonamido)phthalocyanine, X-copper phthalocyanine pigment listed in the
Color Index as CI 74160, CI Pigment Blue, and Anthrathrene Blue,
identified in the Color Index as CI 69810, Special Blue X-2137, and the
like; while illustrative examples of yellow pigments that may be selected
are diarylide yellow 3,3-dichlorobenzidene acetoacetanilides, a monoazo
pigment identified in the Color Index as CI 12700, CI Solvent Yellow 16, a
nitrophenyl amine sulfonamide identified in the Color Index as Foron
Yellow SE/GLN, CI Dispersed Yellow 33, 2,5-dimethoxy-4-sulfonanilide
phenylazo-4'-chloro-2,5-dimethoxy acetoacetanilide, and Permanent Yellow
FGL. In one embodiment, these colored pigment particles are present in the
toner composition in an amount of from about 2 percent by weight to about
15 percent by weight calculated on the weight of the toner resin
particles.
For the formulation of developer compositions, there are mixed with the
toner particles carrier components, particularly those that are capable of
triboelectrically assuming an opposite polarity to that of the toner
composition. Accordingly, the carrier particles of the present invention
are selected to be of a negative polarity enabling the toner particles,
which are positively charged, to adhere to and surround the carrier
particles. Alternatively, the carrier particles can be selected from among
those having a positive polarity, thus enabling the toner particles, which
are negatively charged, to adhere to the carrier surface. Illustrative
examples of carrier particles include iron powder, steel, nickel, iron,
ferrites, including copper zinc ferrites, and the like. Additionally,
there can be selected as carrier particles nickel berry carriers as
illustrated in U.S. Pat. No. 3,847,604, the disclosure of which is totally
incorporated herein by reference. The selected carrier particles can be
used with or without a coating, the coating generally containing
terpolymers of styrene, methylmethacrylate, and a silane, such as
triethoxy silane, reference U.S. Pat. Nos. 3,526,533 and 3,467,634, the
disclosures of which are totally incorporated herein by reference;
polymethyl methacrylates; other known coatings; and the like. The carrier
particles may also include in the coating, which coating can be present in
one embodiment in an amount of from about 0.1 to about 3 weight percent,
conductive substances such as carbon black in an amount of from about 5 to
about 30 percent by weight. Polymer coatings not in close proximity in the
triboelectric series can also be selected, reference U.S. Pat. Nos.
4,937,166 and 4,935,326, the disclosures of which are totally incorporated
herein by reference, including for example KYNAR.RTM. and
polymethylmethacrylate mixtures (40/60). Coating weights can vary as
indicated herein; generally, however, from about 0.3 to about 2, and
preferably from about 0.5 to about 1.5 weight percent coating weight is
selected.
Furthermore, the diameter of the carrier particles, preferably spherical in
shape, is generally from about 50 microns to about 1,000 and preferably
about 175 microns thereby permitting them to possess sufficient density
and inertia to avoid adherence to the electrostatic images during the
development process. The carrier component can be mixed with the toner
composition in various suitable combinations, such as from about 1 to
about 5 parts per toner to about 100 parts to about 200 parts by weight of
carrier.
The toner composition of the present invention can be prepared by a number
of known methods including extrusion melt blending the toner resin
particles, pigment particles or colorants, and the charge enhancing
additive of the present invention as indicated herein, followed by
mechanical attrition and classification. Other methods include those well
known in the art such as spray drying, melt dispersion, extrusion
processing, dispersion polymerization, and suspension polymerization.
Also, as indicated herein the toner composition without the charge
enhancing additive can be prepared, followed by the addition of surface
treated with charge additive colloidal silicas. Further, other methods of
preparation for the toner are as illustrated herein.
The toner and developer compositions of the present invention may be
selected for use in electrostatographic imaging apparatuses containing
therein conventional photoreceptors. Thus, the toner and developer
compositions of the present invention can be used with layered
photoreceptors that are capable of being charged negatively, such as those
described in U.S. Pat. Nos. 4,265,990; 4,584,253; 4,585,884 and 4,563,408,
the disclosures of which are totally incorporated herein by reference.
Illustrative examples of inorganic photoreceptors that may be selected for
imaging and printing processes include selenium; selenium alloys, such as
selenium arsenic, selenium tellurium and the like; halogen doped selenium
substances; and halogen doped selenium alloys.
The following Examples are being supplied to further define various species
of the present invention, it being noted that these Examples are intended
to illustrate and not limit the scope of the present invention. Parts and
percentages are by weight unless otherwise indicated.
EXAMPLE I
Tin Oxide
A. Preparation of Tetra-n-butylstannate
Tin tetrachloride (25 milliliters, obtained from Aldrich Chemical Company)
dissolved in dry toluene (200 milliliters) was added over 80 minutes to a
solution of n-butanol (156 milliliters, obtained from BDH Chemicals) in
dry toluene (300 milliliters) retained under an atmosphere of nitrogen.
The mixture was stirred at room temperature, about 25.degree. C., for 2
hours, after which time dry gaseous ammonia was bubbled for from about 15
minutes to about 5 hours into the solution to render it alkaline as
determined with a pH sensitive paper. The white suspension that formed was
allowed to settle. The supernatant was drawn off by means of a 100
milliliter syringe. Residual toluene solvent was removed by evaporation
under vacuum by means of a rotary evaporator. The residual material was
dried under high vacuum for 24 hours to yield 46.6 grams (53 percent
yield) of tetra-n-butylstannate.
B. Preparation of Coated Tin Oxide
Water (7.5 milliliters) was added to a solution of TRITON X-114.RTM.
surfactant (10 grams, obtained from Rohm and Haas Company) in cyclohexane
(21 milliliters). A thick gel formed immediately. The mixture was stirred
at room temperature for 2 hours, after which tetra-n-butylstannate (2.760
grams, obtained from the preparation described in Example I, part A) in
cyclohexane (17 milliliters) was added dropwise over a period of 5
minutes. The reaction mixture was stirred overnight (18 hours), after
which it was poured into 300 milliliters of acetone, resulting in
formation of a fine white flocculate. The flocculate was separated by
filtration, washed with acetone, and dried in vacuo at 30.degree. C. for
24 hours to yield 0.57 gram of a white solid. The particle size was 5
nanometers, as measured by transmission electron microscopy. The specific
gravity of the sample, which was comprised of tin oxide and TRITON
X-114.RTM., was 3.205 grams per cm.sup.3 as measured with a Micromeritics
Autopycnometer. The specific gravity of a sample of tin oxide produced by
a known flame hydrolysis process was 6.95 grams per cm.sup.3. In view of
the lower specific gravity, 3.205 grams per cm.sup.3 of the tin oxide
coated with surfactant, it is calculated that a lower amount of tin oxide
additive, such as 0.8 percent by weight, can be selected to achieve the
same flow properties of the toner composition, compared to that of a toner
composition with an amount of 2.0 percent by weight of a tin oxide
prepared by a flame hydrolysis process with no surfactant coating.
EXAMPLE II
Tin Oxide
A. Preparation of Tetra-(isopropyl)stannate
Tin tetrachloride (37.5 milliliters, obtained from Aldrich Chemical
Company) dissolved in dry toluene (250 milliliters) was added over 10
minutes to a solution of isopropanol (200 milliliters, obtained from
Caledon and purified by distillation over magnesium turnings) in dry
toluene (500 milliters) kept at 10.degree. C. under an atmosphere of
nitrogen. The mixture was stirred at 10.degree. C. for 75 minutes, after
which time dry gaseous ammonia was bubbled into the solution to render it
alkaline. A white suspension formed. It was allowed to settle. The
supernatant was drawn off by means of a double-ended needle. Residual
solvent was removed by evaporation under vacuum by means of a rotary
evaporator. The residual material was dried under high vacuum for 24 hours
to yield 32.2 grams (28 percent yield) of tetra-(isopropyl)stannate.
B. Preparation of Tin Oxide Coated With Surfactant
Water (6.8 milliliters) was added to a solution of AOT.RTM. surfactant
(32.84 grams, obtained from Aldrich Chemical Company) in toluene (82
milliliters). A thick gel formed immediately. The mixture was stirred at
room temperature for 15 minutes, after which tetra-(isopropyl)stannate
(8.87 grams, obtained from the preparation described in Example II, part
A) in toluene (82 milliliters) was added dropwise over a period of 5
minutes. The reaction mixture was stirred for three days after which it
was poured into 8,500 milliliters of acetone resulting in formation of a
fine white flocculate. The flocculate was separated by filtration, washed
with acetone, and dried in vacuum at 65.degree. C. for 24 hours to yield
5.13 grams of a white-cream colored solid which was comprised of tin oxide
and AOT.RTM.. The particle size was 4 to 5 nanometers, as measured by
transmission electron microscopy. The specific gravity of the product was
4.418 grams per cubic centimeter, as measured with a Micromeritics
Autopycnometer. The specific gravity of a sample of tin oxide produced,
for example, by flame hydrolysis process was 6.95 grams per cubic
centimeter.
EXAMPLE III
Titanium Oxide
Water (11.7 milliliters) was added to a solution of AOT.RTM. surfactant
(56.5 grams, obtained from Aldrich Chemical Company) in toluene (280
milliliters). A thick gel formed immediately. The mixture was stirred at
room temperature for 45 minutes, after which tetra-n-butyl titanate (14.25
milliliters, obtained from Johnson Matthey) was added dropwise over a
period of 5 minutes. The reaction mixture was stirred overnight, after
which it was poured into 700 milliliters of acetone resulting in formation
of a fine light cream colored flocculate. The flocculate was separated by
filtration, washed with acetone, and dried in vacuum at 65.degree. C. for
24 hours to yield 9.35 grams of a white-cream colored solid comprised of
titanium oxide and AOT.RTM.. The particle size was 9 to 10 nanometers as
measured by transmission electron microscopy. The specific gravity of the
product was 1.464 grams per cubic centimeter, as measured with a
Micromeritics Autopycnometer. The specific gravity of a sample of titanium
dioxide obtained by the flame hydrolysis process, such as P25 available
fron Degussa, was 4.0 grams per cubic centimeter.
EXAMPLE IV
Titanium Oxide
Water (11.7 milliliters) was added to a solution of AOT.RTM. surfactant
(56.5 grams, obtained from Aldrich Chemical Company) in toluene (280
milliliters). A thick gel formed immediately. The mixture was stirred at
room temperature for 45 minutes, after which tetra-n-butyl titanate (14.25
milliliters, obtained from Johnson Matthey) was added dropwise over a
period of 5 minutes. The reaction mixture was stirred for eight days at
room temperature after which it was poured into 700 milliliters of acetone
resulting in formation of a fine light cream colored flocculate. The
flocculate was separated by filtration, washed with acetone, and dried in
vacuum at 65.degree. C. for 24 hours to yield 12.14 grams of a white-cream
colored solid comprised of titanium oxide and AOT.RTM.. The particle size
was 9 to 10 nanometers, as measured by transmission electron microscopy.
The specific gravity of this product was 1.479 grams per cubic centimeter,
as measured with a Micromeritics Autopycnometer. The specific gravity of a
sample of titanium dioxide obtained by the flame hydrolysis process, such
as P25.RTM. available from Degussa, was 4.0 grams per cubic centimeter.
EXAMPLE V
Titanium Oxide
Water (82.7 milliliters) was added to a solution of TRITON X-114.RTM.
surfactant (82.7 grams, obtained from Rohm and Haas) in cyclohexane (425
milliliters). A thick gel formed immediately. The mixture was stirred at
room temperature for 45 minutes, after which tetra-n-butyl titanate (29.0
milliliters, obtained from Johnson Matthey) was added dropwise over a
period of 5 minutes. The reaction mixture was stirred overnight at room
temperature after which it was poured into 1,500 milliliters of acetone
resulting in formation of a fine light cream colored flocculate. The
flocculate was separated by filtration, washed with acetone, and dried in
vacuum at 65.degree. C. for 24 hours to yield 10.83 grams of a white-cream
colored solid comprised of titanium oxide and TRITON X-114.RTM.. The
particle size was 9 to 10 nanometers, as measured by transmission electron
microscopy. The specific gravity of the product was 1.980 grams per cubic
centimeter, as measured with a Micromeritics Autopycnometer. The specific
gravity of a sample of the titanium dioxide obtained by the flame
hydrolysis process, such as P25.RTM. available from Degussa, was 4.0 grams
per cubic centimeter.
EXAMPLE VI
Titanium Oxide
Water (41.8 milliliters) was added to a solution of TRITON X-114.RTM.
surfactant (41.8 grams, obtained from Rohm and Haas) in cyclohexane (213
milliliters). A thick gel formed immediately. The mixture was stirred at
room temperature for 45 minutes, after which tetra-n-butyl titanate (29.5
milliliters, obtained from Johnson Matthey) was added dropwise over a
period of 5 minutes. The reaction mixture was stirred overnight at room
temperature after which it was poured into 1,700 milliliters of acetone
resulting in formation of a fine light cream colored flocculate. The
flocculate was separated by filtration, washed with acetone, and dried in
vacuum at 65.degree. C. for 24 hours to yield 10.61 grams of a white-cream
colored solid comprised of titanium oxide and TRITON X-114.RTM.. The
particle size was 9 to 10 nanometers, as measured by transmission electron
microscopy. The specific gravity of the product was 1.956 grams per cubic
centimeter, as measured with a Micromeritics Autopycnometer. The specific
gravity of a sample of titanium dioxide obtained by the flame hydrolysis
process, such as P25.RTM. available from Degussa, was 4.0 grams per cubic
centimeter.
EXAMPLE VII
Zirconium Oxide
Water (17.7 milliliters) was added to a solution of TRITON X-114.RTM.
surfactant (17.7 grams, obtained from Rohm and Haas) in cyclohexane (90
milliliters). A thick gel formed immediately. The mixture was stirred at
room temperature for 60 minutes, after which tetra-n-butyl zirconate,
butanol complex (16.0 milliliters, obtained from Alfa Company) was added
dropwise over a period of 5 minutes. The reaction mixture was stirred
overnight at room temperature, after which it was poured into 900
milliliters of acetone, resulting in formation of a fine light cream
colored flocculate. The flocculate was separated by filtration, washed
with acetone, and dried in vacuum at 65.degree. C. for 24 hours to yield
6.535 grams of a white-cream colored solid comprised of zirconium oxide
and TRITON X-114.RTM.. The particle size was 4 to 5 nanometers as measured
by transmission electron microscopy. The specific gravity of the product
sample was 3.809 grams per cubic centimeter, as measured with a
Micromeritics Autopycnometer.
EXAMPLE VIII
Zirconium Oxide
Water (35.0 milliliters) was added to a solution of TRITON X-114.RTM.
surfactant (35.0 grams, obtained from Rohm and Haas) in cyclohexane (180
milliliters). A thick gel formed immediately. The mixture was stirred at
room temperature for 60 minutes, after which tetra-n-butyl zirconate,
butanol complex (16.0 milliliters, obtained from Alfa Company) was added
dropwise over a period of 5 minutes. The reaction mixture was stirred
overnight at room temperature, after which it was poured into 900
milliliters of acetone resulting in formation of a fine light cream
colored flocculate. The flocculate was separated by filtration, washed
with acetone, and dried in vacuum at 65.degree. C. for 24 hours to yield
6.698 grams of a white-cream colored solid comprised of zirconium oxide
and TRITON X-114.RTM.. The particle size was 4 to 5 nanometers, as
measured by transmission electron microscopy. The specific gravity of the
product was 2.551 grams per cubic centimeter, as measured with a
Micromeritics Autopycnometer.
EXAMPLE IX
Zirconium Oxide
Water (4.55 milliliters) was added to a solution of AOT.RTM. surfactant
(22.0 grams, dioctyl succinate, sodium salt, obtained from Aldrich
Chemical Company) in toluene (110 milliliters). A thick gel formed
immediately. The mixture was stirred at room temperature for 90 minutes,
after which tetra-n-butyl zirconate, butanol complex (7.4 milliliters,
obtained from Johnson Matthey) was added dropwise over a period of 5
minutes. The reaction mixture was stirred for 24 hours at room
temperature, after which it was poured into 900 milliliters of acetone
resulting in formation of a fine light cream colored flocculate. The
flocculate was separated by filtration, washed with acetone, and dried in
vacuum at 65.degree. C. for 24 hours to yield 5.21 grams of a white-cream
colored solid comprised of zirconium oxide and AOT.RTM.. The particle size
was 5 nanometers, as measured by transmission electron microscopy. The
specific gravity of the product was 1,770 grams per cubic centimeter, as
measured with a Micromeritics Autopycnometer.
EXAMPLE X
Zirconium Oxide
Water (4.05 milliliters) was added to a solution of AOT.RTM. surfactant
(22.0 grams, obtained from Aldrich Chemical Company) in toluene (280
milliliters). A thick gel formed immediately. The mixture was stirred at
room temperature for 45 minutes, after which tetra-n-butyl zirconate,
butanol complex (7.4 milliliters, obtained from Johnson Matthey) was added
dropwise over a period of 5 minutes. The reaction mixture was stirred for
eight days at room temperature, after which it was poured into 450
milliliters of acetone resulting in formation of a fine light cream
colored flocculate. The flocculate was separated by filtration, washed
with acetone, and dried in vacuum at 65.degree. C. for 24 hours to yield
6.87 grams of a white-cream colored solid comprised of zirconium oxide and
AOT.RTM.. The particle size was 6 to 7 nanometers, as measured by
transmission electron microscopy. The specific gravity of the product was
1.733 grams per cubic centimeter as measured with a Micromeritics
Autopycnometer.
EXAMPLE XI
Silica
A solution of concentrated ammonium hydroxide (1.8 milliliters, 14
milliliters in water) and water (6.5 milliliters) was added to a solution
of AOT.RTM. surfactant (40.0 grams, obtained from Aldrich Chemical
Company) in toluene (200 milliliters). A thick gel formed immediately. The
mixture was stirred at room temperature for 45 minutes, after which
tetraethoxysilane (6.8 milliliters, obtained from Aldrich Chemical
Company) was added dropwise over a period of 5 minutes. The reaction
mixture was stirred for three days at room temperature, after which it was
poured into 300 milliliters of acetone resulting in formation of a fine
white colored flocculate. The flocculate was separated by filtration,
washed with acetone, and dried in vacuum at 65.degree. C. for 24 hours to
yield 1.508 grams of a white-cream colored solid comprised of silica and
AOT.RTM.. The particle size was 14 to 16 nanometers, as measured by
transmission electron microscopy.
EXAMPLE X
Silica
A solution of concentrated ammonium hydroxide (18.5 milliliters, 14
milliliters in water) and water (9.3 milliliters) was added to a solution
of ALKASURF OP-8.RTM. surfactant (28.0 grams, obtained from Alkaril
Chemicals Ltd.) in cyclohexane (140 milliliters). A thick gel formed
immediately. The mixture was stirred at room temperature for 45 minutes,
after which tetraethoxysilane (5.6 milliliters, obtained from Aldrich
Chemical Company) was added dropwise over a period of 5 minutes. The
reaction mixture was stirred for 24 hours at room temperature, after which
it was poured into 300 milliliters of acetone resulting in formation of a
fine white colored flocculate. The flocculate was separated by filtration,
washed with acetone, and dried in vacuum at 65.degree. C. for 24 hours to
yield 1.708 grams of a white-cream colored solid comprised of silica and
ALKASURF OP-8.RTM.. The particle size was 14 to 16 nanometers as measured
by transmission electron microscopy.
EXAMPLE XI
Silica
A solution of concentrated ammonium hydroxide (18.5 milliliters, 14
milliliters in water) and water (9.3 milliliters) was added to a solution
of ALKASURF NP-8.RTM. surfactant (28.0 grams, obtained from Alkaril
Chemicals Ltd.) in cyclohexane (140 milliliters). A thick gel formed
immediately. The mixture was stirred at room temperature for 45 minutes,
after which tetraethoxysilane (5.6 milliliters, obtained from Aldrich
Chemical Company) was added dropwise over a period of 5 minutes. The
reaction mixture was stirred for 24 hours at room temperature, after which
it was poured into 300 milliliters of acetone resulting in formation of a
fine white colored flocculate. The flocculate was separated by filtration,
washed with acetone, and dried in vacuum at 65.degree. C. for 24 hours to
yield 1.731 grams of a white-cream colored solid comprised of silica and
ALKASURF NP-8.RTM.. The particle size was 14 to 16 nanometers as measured
by transmission electron microscopy.
EXAMPLE XII
Toner Composition
A toner composition was prepared by mixing 10 grams of a toner comprised of
93.5 percent by weight of a resin comprised of 50 percent by weight of
styrene and 50 percent by weight of n-butyl methacrylate, 6 percent by
weight of REGAL 330.RTM. carbon black, and 0.5 percent by weight of cetyl
pyridinium chloride with 20 milligrams of the tin oxide with surfactant
prepared according to the procedure of Example I in a blender equipped
with a blade moving at a speed of 88 m/s for 15 seconds. The final toner
composition comprised of 0.2 percent by weight of tin oxide with
surfactant and 99.8 percent of toner. The flow of the toner was determined
by measuring the percent cohesion of the toner by means of a Hosokawa
Micron Powder Characteristics Tester. The percent cohesion is proportional
to the fraction of the toner that will not flow under the conditions of
the standard test. A lower percent cohesion indicates better flow
properties. The cohesion of the resulting toner was 8.3 percent at a
relative humidity of 50 percent, as measured by means of a Hosokawa Micron
Powder Characteristics Tester. The cohesion of the same toner composition
with no tin oxide flow additive measured under the same conditions was 13
percent. The lower cohesion value of the toner treated with the tin oxide
with surfactant additive is indicative of a 56 percent improvement in
flow, as determined by means of a Hosokawa Micron Powder Characteristics
Tester. The cohesion value of a toner of identical composition treated
under the same conditions with 0.2 percent by weight of a sample of tin
oxide without surfactant with a particle size of 9 nanometers prepared by
a flame hydrolysis process was 9.7 percent. This result is indicative of
the superior flow of a toner treated with the tin oxide prepared according
to the procedure of Example I compared to a toner treated with the same
weight percent of tin oxide prepared by the known flame hydrolysis
process.
EXAMPLE XIII
Toner Composition
A toner composition was prepared by mixing 10 grams of a toner consisting
of 93.5 percent by weight of a resin composed of 50 percent by weight of
styrene and 50 percent by weight of n-butyl methacrylate, 6 percent by
weight of REGAL 330.RTM. carbon black, and 0.5 percent by weight of cetyl
pyridinium chloride with 30 milligrams of the tin oxide prepared according
to the procedure of Example I in a blender equipped with a blade moving at
a speed of 88 m/s for 15 seconds. The flow of the toner was determined by
measuring the percent cohesion of the toner by means of a Hosokawa Micron
Powder Characteristics Tester. The percent cohesion is proportional to the
fraction of the toner that will not flow under the conditions of the
standard test. A lower percent cohesion indicates better flow properties.
The cohesion of the resulting toner was 6.3 percent at a relative humidity
of 50 percent, as measured by means of a Hosokawa Micron Powder
Characteristics Tester. The cohesion of the same toner composition with no
flow additive measured under the same conditions was 13 percent. The lower
cohesion value of the toner treated with the metal oxide and surfactant
additive is indicative of a 100 percent improvement in toner flow, as
determined by means of a Hosokawa Micron Powder Characteristics Tester.
EXAMPLE XIV
Toner Composition
A toner composition was prepared by mixing 10 grams of a toner consisting
of 93.5 percent by weight of a resin composed of 50 percent by weight of
styrene and 50 percent by weight of n-butyl methacrylate, 6 percent by
weight of REGAL 330.RTM. carbon black, and 0.5 percent by weight of cetyl
pyridinium chloride with 80 milligrams of the tin oxide prepared according
to the procedure of Example II in a blender equipped with a blade moving
at a speed of 88 m/s for 15 seconds. The cohesion of the resulting toner
was 7.1 percent at a relative humidity of 50 percent, as measured by means
of a Hosokawa Micron Powder Characteristics Tester. The cohesion of the
same toner composition with no flow additive measured under the same
conditions was 13 percent. The lower cohesion value of the toner treated
with the metal oxide and surfactant additive is indicative of a 85 percent
improvement in toner flow as determined by means of a Hosokawa Micron
Powder Characteristics Tester.
EXAMPLE XV
A developer composition was prepared by admixing for 15 minutes 1 gram of a
toner comprised of 0.2 percent by weight of tin oxide on the surface
prepared according to the procedure described in Example I and 99.8
percent of a toner comprised of 90 percent by weight of a resin composed
of 50 percent by weight of styrene and 50 percent by weight of n-butyl
methacrylate, and 10 percent by weight of RAVEN 5750.RTM. carbon black
with 49.0 grams of a carrier comprised of 100 microns (average diameter)
ferrite particles coated with a terpolymer consisting of 81 percent by
weight of methyl methacrylate, 14 percent by weight of styrene, and 5
percent by weight of vinyl triethoxysilane. There resulted on the toner
composition a negative tribolectric charge of 27.5 microcoulombs per gram.
The tribolectric charge of an untreated toner charged under the same
conditions was -26.4 microcoulombs per gram. This result indicates that
the tin oxide additive does not modify significantly the triboelectric
charge of the toner composition to which it is added in an amount
sufficient for marked improvement in the flow properties of the toner as
indicated, for example, in Example XIII.
EXAMPLE XVI
A developer composition was prepared by admixing for 15 minutes 1 gram of a
toner composed of 0.2 percent by weight of tin oxide prepared according to
the procedure described in Example II and 99.8 percent of a toner
consisting of 90 percent by weight of a resin composed of 50 percent by
weight of styrene and 50 percent by weight of n-butyl methacrylate, and 10
percent by weight of RAVEN 5750.RTM. carbon black with 49.0 grams of a
carrier consisting of 100 microns of ferrite particles coated with a
terpolymer consisting of 81 percent by weight of methyl methacrylate, 14
percent by weight of styrene, and 5 percent by weight of vinyl
triethoxysilane. There resulted on the toner composition a negative
triboelectric charge of 26.3 microcoulombs per gram. The tribolectric
charge of an untreated toner charged under the same conditions was -26.4
microcoulombs per gram.
Other modifications of the present invention may occur to those skilled in
the art subsequent to a review of the present application, and these
modifications, including equivalents thereof, are intended to be included
within the scope of the present invention.
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